Electromagnetic relays and contactors operating in contaminated atmospheres occasionally experience welding of the contacts over a period of time in use. This problem may result from mounting of the device so that a clapper armature is disposed in a vertical plane and is mounted for pivotal movement about a line of engagement with a straight edge of the magnetic yoke in a manner which permits falling dust and dirt to collect in the armature pivot area. The dirt may accumulate to the point where interference occurs between the armature and the edge of the yoke and prevents the armature from closing completely, and such interference may result in loss of contact pressure, increased contact heating and welding of the contacts. Further, such accumulation of dirt adjacent the armature pivot area may cause the pivoted end of the armature to move in a direction away from the yoke during closing rather than pivoting about the line of engagement with the yoke. Such undesired movement of the pivoted end of the armature may introduce a high reluctance air gap in the magnetic circuit which accentuates the problems of increased contact heating and welding of the contacts.